Stainless steel 420 420
Iron-chromium-carbon steel: Fe balance, Cr 12.0 to 14.0 %, C 0.16 to 0.25 % (EN 1.4021 composition)
Also known as UNS S42000, EN 1.4021, EN name X20Cr13, AISI 420, ASTM A276, ASTM A484 · 1 more
AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon (EN composition).
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Carry load when hard
255.2 ksi tensile
Stay hard
48 HRC
Soft to form
241 HB maximum
Weight
7.75 g/cm3
Heat to 675 °C
675 °C continuous
Recipe, share of the weight
- Fe not statedIron
- Cr not statedChromium
- C not statedCarbon
- Mn not statedManganese
- Si not statedSilicon
- S not statedSulphur
Best for
Hardened wear parts, blades and bearing-type components that need high strength and edge retention, from one steel that reaches 48 HRC after tempering at 440 °F
Weakest at
Corrosion resistance and ductility: it resists corrosion less well than austenitic grades, and it loses strength when tempered at 1000 °F (158.5 ksi tensile)
Risk at a glance
- People Low. Low for solid stock, higher for dust and fume
- If it fails High. Loss of strength from over-tempering
- Corrosion Moderate. Martensitic steels resist corrosion less well than ferritic and austenitic grades because their chromium is low.
Quick facts: 420
| Property | Value | Basis |
|---|---|---|
| Density | 7.7 to 7.75 g/cm³ | 3 sourced values across conditions |
| Yield strength | 355 to 1,311 MPa | 5 sourced values across conditions |
| Tensile strength | 592 to 1,760 MPa | 5 sourced values across conditions |
| Young's modulus | 200 to 215 GPa | 3 sourced values across conditions |
| Hardness (Brinell) | 230 to 241 HB | 2 sourced values across conditions |
| Thermal conductivity | 24.9 to 30 W/(m·K) | 2 sourced values across conditions |
| Thermal expansion (CTE) | 10.3 ppm/K | 1 sourced value |
| Melting point | 1,454 to 1,510 °C | 1 sourced value |
| Specific heat | 460 J/(kg·K) | 1 sourced value |
| Electrical resistivity | 5.5e-7 Ω·m | 3 sourced values across conditions |
| Maximum service temperature | 675 °C | 1 sourced value |
What is the density of Stainless steel 420?
Stainless steel 420 has a density of 7.7 to 7.75 g/cm³. The range covers 3 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the thermal conductivity of Stainless steel 420?
Stainless steel 420 has a thermal conductivity of 24.9 to 30 W/(m·K). The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the coefficient of thermal expansion of Stainless steel 420?
Stainless steel 420 has a coefficient of thermal expansion of 10.3 ppm/K. The source and test conditions are listed in the properties table on this page.
What is the melting point of Stainless steel 420?
Stainless steel 420 has a melting point of 1,454 to 1,510 °C. The source and test conditions are listed in the properties table on this page.
What is the yield strength of Stainless steel 420?
Stainless steel 420 has a yield strength of 355 to 1,311 MPa. The range covers 5 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What are the other names and codes for Stainless steel 420?
Stainless steel 420 is also written as UNS S42000, EN 1.4021, EN name X20Cr13, AISI 420, ASTM A276, ASTM A484. Each code is printed in the source listed beside it in the designations table.
What is Stainless steel 420 used for?
Uses recorded in the sources include Bearings and industrial chains; Pumps and valves.
Why it exists
AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon. The carbon lets it be hardened, so it reaches about 48 HRC after tempering at 440 °F (Rolled Alloys), while annealed it is soft, at most 241 HB. Its density is 7.75 g/cm3, and it is magnetic. It is chosen where a steel must be hard and wear-resistant and still stainless enough for blades, chains, bearings and valves. Its weak points are corrosion resistance, which is lower than that of austenitic steels, and strength loss if it is over-tempered.
Where it's used
Bearings and chains
Rolled Alloys lists industrial chains and bearings among the applications of Type 420, which is used for high strength, high wear resistance or good edge retention.
Pumps and valves
Rolled Alloys lists pumps and valves, and plastic injection moulds and dies, among the applications of Type 420.
Recipe
Iron-chromium-carbon steel: Fe balance, Cr 12.0 to 14.0 %, C 0.16 to 0.25 % (EN 1.4021 composition)
Martensitic stainless steel of iron with about 12 to 14 % chromium and 0.16 to 0.25 % carbon (EN 1.4021 composition). The steel is hot-worked after uniform heating to 1149 to 1232 °C (Aalco), then hardened and tempered (teamedelstahl).
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Iron Fe | not stated | Matrix of the steel |
| Chromium Cr | not stated | Gives the steel its stainless character; low chromium makes it less corrosion-resistant than ferritic and austenitic grades (Wikipedia) |
| Carbon C | not stated | Makes the steel hardenable; gives higher heat-treated strength at some cost in ductility (Rolled Alloys) |
| Manganese Mn | not stated | Maximum allowed in the composition (teamedelstahl composition table) |
| Silicon Si | not stated | Maximum allowed in the composition (teamedelstahl composition table) |
| Sulphur S | not stated | Limit on the impurity; Aalco describes its bar as sulphur-enhanced for machining |
Weight shares are as printed in the sources.
What it can do
Carry load when hard
255.2 ksi tensile
measured
Tempered at 440 °F, Type 420 has a tensile strength of 255.2 ksi and a yield strength of 190.1 ksi (Rolled Alloys tempered-condition table).
Stay hard
48 HRC
measured
The same tempered condition gives 48 HRC. Tempering at 1000 °F drops this to 36 HRC.
Soft to form
241 HB maximum
measured
Annealed (Condition A), the maximum hardness is 241 HB, and the yield strength is 51.5 ksi.
Weight
7.75 g/cm3
measured
Density is 7.75 g/cm3 in the Aalco datasheet, and 7.7 kg/dm3 at 20 °C in the teamedelstahl page.
Heat to 675 °C
675 °C continuous
measured
Aalco gives a scaling limit of 675 °C continuous and 760 °C intermittent. This is a scaling limit; above the tempering temperature the mechanical properties fall.
How it compares
Among the stainless steels, 420 trades corrosion resistance for hardness: Wikipedia says martensitic steels are less corrosion-resistant than ferritic and austenitic grades. Its density of 7.75 g/cm3 (Aalco) is close to the value of 7.7 kg/dm3 given by teamedelstahl for the same grade. The compare rows use the figures printed by the sources, not a ranking of different alloys.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | 420 | 410 (UNS S41000) | 440C (UNS S44004) | S41500 (F6NM forged, CA6NM cast) | 410S (UNS S41008) | 416 | 431 (UNS S43100, EN 1.4057) | 1.4418 (X4CrNiMo16-5-1) |
|---|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | ||||||||
| Melting range, Type 420Range printed in a mill datasheet | 2650 to 2750 °F | 1482 to 1532 °C | 2500 to 2700 °F | no data | 1480 to 1530 °C | 2714 °F | no data | no data |
| Thermal conductivity, 1.4021 barValue printed in a stockholder datasheet | 24.9 W/(m·K) | 24.9 W/m-K | 24.2 W/m.K | 25 W/(m K) | 26.9 W/m-K | 30 W/m K | 25 W/(m·K) | 15 W/m K |
| Thermal conductivity, 1.4021 (20 °C) | 30 W/(m·K)5 | 24.9 W/m-K | 24.2 W/m.K | 25 W/(m K) | 26.9 W/m-K | 30 W/m K | 25 W/(m·K) | 15 W/m K |
| Thermal conductivity, Type 420 (212 °F)Value printed in a mill datasheet | 14.4 BTU/(hr·ft·°F) | 24.9 W/m-K | 24.2 W/m.K | 25 W/(m K) | 26.9 W/m-K | 30 W/m K | 25 W/(m·K) | 15 W/m K |
| Specific heat capacity, 1.4021 (20 °C) | 460 J/(kg·K)6 | 0.46 kJ/(kg·K) | no data | 430 J/(kg K) | 0.46 kJ/kg·K | 460 J/kg K | 460 J/(kg·K) | 430 J/kg K |
| Physical and electrical | ||||||||
| Density, 1.4021 bar (EN 10088-3)Value printed in a stockholder datasheet | 7.75 g/cm³1 | 7.73 g/cm³ | 0.275 lb/in3 | 7.61 to 8.1 kg/dm3 | 7.73 g/cm³ | 7.7 kg/dm3 | 7800 kg/m3 | 7.7 kg/dm3 |
| Density, 1.4021 / AISI 420 (20 °C) | 7.7 kg/dm32 | 7.73 g/cm³ | 0.275 lb/in3 | 7.61 to 8.1 kg/dm3 | 7.73 g/cm³ | 7.7 kg/dm3 | 7800 kg/m3 | 7.7 kg/dm3 |
| Density, Type 420 (ASTM A276)Value printed in a mill datasheet | 0.278 lb/in3 | 7.73 g/cm³ | 0.275 lb/in3 | 7.61 to 8.1 kg/dm3 | 7.73 g/cm³ | 7.7 kg/dm3 | 7800 kg/m3 | 7.7 kg/dm3 |
| Electrical resistivity, 1.4021 barValue printed in a stockholder datasheet | 0.55 µΩ·m7 | 57 µohm-cm | 0.6 10-6 ohm.m | no data | 60 µohm-cm | 0.6 Ω mm2/m | 0.7 ohm mm2/m | no data |
| Electrical resistivity, 1.4021 (20 °C) | 0.6 Ω·mm2/m8 | 57 µohm-cm | 0.6 10-6 ohm.m | no data | 60 µohm-cm | 0.6 Ω mm2/m | 0.7 ohm mm2/m | no data |
| Electrical resistivity, Type 420Value printed in a mill datasheet | 25.6 µΩ·in | 57 µohm-cm | 0.6 10-6 ohm.m | no data | 60 µohm-cm | 0.6 Ω mm2/m | 0.7 ohm mm2/m | no data |
| Hardness Brinell maximum, Type 420 annealed (Condition A)Maximum value printed in a mill datasheet | < 241 HB | no data | no data | no data | no data | < 220 HB | 260 HB | no data |
| Hardness Brinell maximum, 1.4021 (20 °C) | < 230 HB21 | no data | no data | no data | no data | < 220 HB | 260 HB | no data |
| Hardness Rockwell C, Type 420 tempered at 440 °F | 48 HRC22 | no data | no data | no data | no data | 26 to 32 RC | no data | no data |
| Hardness Rockwell C, Type 420 tempered at 1000 °F | 36 HRC23 | no data | no data | no data | no data | 26 to 32 RC | no data | no data |
| Other measurements | ||||||||
| Poisson's ratio, Type 420Value printed in a mill datasheet | 0.28 - | 0.28 - | 0.3 - | 0.27 to 0.3 - | no data | no data | no data | no data |
| Modulus of elasticity, 1.4021 barValue printed in a stockholder datasheet | 200 GPa3 | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 215 kN/mm2 | 200 GPa |
| Modulus of elasticity, 1.4021 (20 °C) | 215 kN/mm24 | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 215 kN/mm2 | 200 GPa |
| Modulus of elasticity, Type 420 (68 °F)Value printed in a mill datasheet | 31.2 10^6 psi | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 200 GPa | 215 kN/mm2 | 200 GPa |
| Coefficient of thermal expansion, 1.4021 bar (0 to 100 °C)Value printed in a stockholder datasheet | 10.3 10^-6/K | 9.9 µm/m-°C | 10.1 10-6/K | no data | 10.8 µm/m·K | 10.5 10^-6/K | 10 ppm/K | 10.8 10-6 K-1 |
| Coefficient of thermal expansion, Type 420 (68 to 212 °F)Value printed in a mill datasheet | 5.833 µin/in·°F | 9.9 µm/m-°C | 10.1 10-6/K | no data | 10.8 µm/m·K | 10.5 10^-6/K | 10 ppm/K | 10.8 10-6 K-1 |
| Yield strength 0.2 % offset, Type 420 annealed (Condition A) | 51.5 ksi9 | 205 to 290 MPa | 1896 MPa | > 520 MPa | > 30 ksi | > 450 MPa | 600 MPa | > 550 MPa |
| Yield strength 0.2 % offset, Type 420 tempered at 440 °F | 190.1 ksi10 | 205 to 290 MPa | 1896 MPa | > 520 MPa | > 30 ksi | > 450 MPa | 600 MPa | > 550 MPa |
| Yield strength 0.2 % offset, Type 420 tempered at 1000 °F | 137.9 ksi11 | 205 to 290 MPa | 1896 MPa | > 520 MPa | > 30 ksi | > 450 MPa | 600 MPa | > 550 MPa |
| Proof stress Rp0.2, 1.4021 bar up to 160 mmRange printed in a stockholder datasheet | 500 to 600 MPa12 | 205 to 290 MPa | 1896 MPa | > 520 MPa | > 30 ksi | > 450 MPa | 600 MPa | > 550 MPa |
| Yield strength Rp0.2, 1.4021 (20 °C) lower limit | > 460 N/mm213 | 205 to 290 MPa | 1896 MPa | > 520 MPa | > 30 ksi | > 450 MPa | 600 MPa | > 550 MPa |
| Tensile strength, Type 420 annealed (Condition A) | 85.8 ksi14 | 450 to 510 MPa | 1965 MPa | < 1100 MPa | > 60 ksi | 650 to 850 N/mm2 | 862 MPa | 760 to 960 MPa |
| Tensile strength, Type 420 tempered at 440 °F | 255.2 ksi15 | 450 to 510 MPa | 1965 MPa | < 1100 MPa | > 60 ksi | 650 to 850 N/mm2 | 862 MPa | 760 to 960 MPa |
| Tensile strength, Type 420 tempered at 1000 °F | 158.5 ksi16 | 450 to 510 MPa | 1965 MPa | < 1100 MPa | > 60 ksi | 650 to 850 N/mm2 | 862 MPa | 760 to 960 MPa |
| Tensile strength Rm, 1.4021 bar up to 160 mmRange printed in a stockholder datasheet | 700 to 950 MPa17 | 450 to 510 MPa | 1965 MPa | < 1100 MPa | > 60 ksi | 650 to 850 N/mm2 | 862 MPa | 760 to 960 MPa |
| Tensile strength Rm, 1.4021 (20 °C) | 750 to 850 N/mm218 | 450 to 510 MPa | 1965 MPa | < 1100 MPa | > 60 ksi | 650 to 850 N/mm2 | 862 MPa | 760 to 960 MPa |
| Elongation A, 1.4021 bar up to 160 mmRange printed in a stockholder datasheet | 12 to 13 %19 | 20 to 34 % | 2 % | 15 % | > 22 % | > 12 % | 20 % | > 16 % |
| Elongation A5.65, 1.4021 (20 °C) lower limit | > 12 %20 | 20 to 34 % | 2 % | 15 % | > 22 % | > 12 % | 20 % | > 16 % |
| Scaling resistance limit, continuous (1.4021) | < 675 °C24 | < 649 °C | 400 °C | 300 °C | < 705 °C | 675 °C | 400 °C | 300 °C |
Why choose it, and why not
Good for
- Hard, wear-resistant parts: 48 HRC after tempering at 440 °F (Rolled Alloys).
- Stainless service with a magnetic response: 420 is magnetic in both conditions (Wikipedia).
- Scaling in air up to 675 °C continuous (Aalco).
Watch out for
- Corrosion: lower than that of austenitic grades, and best in the hardened condition (Aalco, Wikipedia).
- Over-tempering at 1000 °F drops tensile strength to 158.5 ksi.
- Sub-zero ductility is lost (Aalco), so brittle failure is a risk in cold service.
- Sources differ on thermal conductivity (24.9 W/(m·K) against 30 W/(m·K)) and modulus (200 GPa against 215 GPa).
AISI 420 (UNS S42000, EN 1.4021) is a hardenable stainless steel for blades, chains, bearings and valves. It reaches 48 HRC when tempered at 440 °F, weighs 7.75 g/cm3 and is magnetic. It resists corrosion less well than austenitic steels and loses strength when over-tempered. This profile lacks a 1.4021-specific corrosion rate, impact values and vacuum data.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Other names and standards
The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.
| System | Codes |
|---|---|
| UNS | S42000 |
| EN | 1.4021 |
| EN name | X20Cr13 |
| AISI | 420 |
| ASTM | A276 (listed specification for Type 420), A484 (listed specification for Type 420) |
| AMS | 5621 |
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, 1.4021 bar (EN 10088-3) | — | grade 1.4021 (420) bar, up to 160 mmstandard EN 10088-3:2005temperature not stated | — |
| 2 | Density, 1.4021 / AISI 420 (20 °C) | Value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °C | — |
| 3 | Modulus of elasticity, 1.4021 bar | — | grade 1.4021 (420) bar, up to 160 mmstandard EN 10088-3:2005temperature not stated | — |
| 4 | Modulus of elasticity, 1.4021 (20 °C) | Value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °C | The other two sources give 200 GPa (Aalco) and 31.2 x 10^6 psi, which is about 215 GPa; the 200 GPa figure is a separate row. |
| 5 | Thermal conductivity, 1.4021 (20 °C) | Value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °C | Two sources differ: 24.9 W/(m·K) (Aalco, temperature not stated) and 30 W/(m·K) at 20 °C (teamedelstahl). Both are kept with their conditions. |
| 6 | Specific heat capacity, 1.4021 (20 °C) | Value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °C | — |
| 7 | Electrical resistivity, 1.4021 bar | — | grade 1.4021 (420) bar, up to 160 mmunit in source x10^-6 Ω.mtemperature not stated | — |
| 8 | Electrical resistivity, 1.4021 (20 °C) | Value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °C | — |
| 9 | Yield strength 0.2 % offset, Type 420 annealed (Condition A) | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper annealed (Condition A, ASTM A276)measure 0.2 % yield strength | — |
| 10 | Yield strength 0.2 % offset, Type 420 tempered at 440 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 440 °Fmeasure 0.2 % yield strength | — |
| 11 | Yield strength 0.2 % offset, Type 420 tempered at 1000 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 1000 °Fmeasure 0.2 % yield strength | Over-tempering: the same table gives 36 HRC at this temper, against 48 HRC at 440 °F. |
| 12 | Proof stress Rp0.2, 1.4021 bar up to 160 mm | — | grade 1.4021 (420) bar, up to 160 mmstandard EN 10088-3:2005temper not stated | — |
| 13 | Yield strength Rp0.2, 1.4021 (20 °C) lower limit | Minimum value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °Ctemper not stated | — |
| 14 | Tensile strength, Type 420 annealed (Condition A) | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper annealed (Condition A, ASTM A276) | — |
| 15 | Tensile strength, Type 420 tempered at 440 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 440 °F | — |
| 16 | Tensile strength, Type 420 tempered at 1000 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 1000 °F | — |
| 17 | Tensile strength Rm, 1.4021 bar up to 160 mm | — | grade 1.4021 (420) bar, up to 160 mmstandard EN 10088-3:2005temper not stated | — |
| 18 | Tensile strength Rm, 1.4021 (20 °C) | Range printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °Ctemper not stated | — |
| 19 | Elongation A, 1.4021 bar up to 160 mm | — | grade 1.4021 (420) bar, up to 160 mmstandard EN 10088-3:2005temper not stated | — |
| 20 | Elongation A5.65, 1.4021 (20 °C) lower limit | Minimum value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °Ctemper not stated | — |
| 21 | Hardness Brinell maximum, 1.4021 (20 °C) | Maximum value printed in a steel supplier's material page | grade 1.4021 (X20Cr13 / AISI 420)temperature 20 °Ctemper not stated | — |
| 22 | Hardness Rockwell C, Type 420 tempered at 440 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 440 °F | — |
| 23 | Hardness Rockwell C, Type 420 tempered at 1000 °F | Value printed in a mill datasheet, tempered-condition table | grade Type 420, UNS S42000temper tempered at 1000 °F | — |
| 24 | Scaling resistance limit, continuous (1.4021) | Value printed in a stockholder datasheet, corrosion resistance section | grade 1.4021 (420)basis scaling resistance, continuousintermittent limit 760 °Cnote in source use above the tempering temperature is not recommended if mechanical properties must be kept | A scaling limit, not a structural service limit. The Aalco page says mechanical properties fall above the tempering temperature. |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Air and humid atmospheres | moderate | Martensitic steels resist corrosion less well than ferritic and austenitic grades because their chromium is low.1 |
| Hardened condition | moderate | Maximum corrosion resistance is reached in the fully hardened condition, not the annealed one.2 |
| High-temperature scaling in air | moderate | 420 scales in air at high temperature, with a continuous limit of 675 °C.3 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Air and humid atmospheres | Wikipedia says martensitic stainless steels are not as corrosion-resistant as ferritic and austenitic grades due to their low chromium content, and lists Type 420 as a representative grade. Rolled Alloys says 420 offers corrosion resistance comparable to that of Type 410. | basis general comparison; no corrosion rate or test environment given in the sources |
| 2 | Hardened condition | Aalco states that maximum corrosion resistance is achieved in the hardened condition, and the Rolled Alloys sheet describes 420 as similar to 410 in corrosion resistance. No corrosion rate is given. | basis qualitative statement; no test environment given |
| 3 | High-temperature scaling in air | Aalco gives fair scaling resistance up to 760 °C intermittently and 675 °C continuously, and says use above the tempering temperature is not recommended if mechanical properties must be kept. | basis scaling resistance in air; no weight-gain or rate values given |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The sources describe a generic stainless steel SDS for solid stock, and the risk comes from dust, fume and processing rather than from the solid.
- Solid stock
- A generic stainless steel SDS says solid metal articles are generally not hazardous materials under the OSHA Hazard Communication Standard. Small chips, fines and dust may ignite readily.
- Processing
- Cutting, grinding and welding can release hazardous elements, and welding or grinding can generate hexavalent chromium. Ventilation is the control the SDS names.
If it fails
The failure routes in the sources are about temper and temperature, not about a single corrosion rate.
- Over-tempering
- Tempered at 1000 °F, 420 falls to 158.5 ksi tensile and 36 HRC, against 255.2 ksi and 48 HRC at 440 °F (Rolled Alloys).
- Sub-zero service
- Aalco says ductility is lost below zero, which limits the useful range.
- Corrosion
- Wikipedia says martensitic steels resist corrosion less well than ferritic and austenitic grades. Aalco says maximum corrosion resistance is reached in the hardened condition.
Handling and storage
- Keep the temper in view
- Strength and hardness follow the tempering temperature. The order should name the temper.
- Welds
- Aalco recommends preheat at 150 to 320 °C and post-heat at 610 to 760 °C for high-strength joints.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Loss of strength from over-temperinghigh severity | Tempering or service at 1000 °F (538 °C)The Rolled Alloys table gives 158.5 ksi tensile and 137.9 ksi yield at 1000 °F, against 255.2 ksi tensile at 440 °F, and 36 HRC against 48 HRC. Aalco also warns of strength loss from over-tempering at elevated temperature. |
| Brittleness at sub-zero temperaturemoderate severity | Service below zero degrees CelsiusAalco says the useful temperature range is limited by loss of ductility below zero. |
| Cracking during hot workingmoderate severity | Hot working below 1700 °F (927 °C)Aalco says hot work below 1700 °F may cause cracking; work should start after uniform heating to 2100 to 2250 °F (1149 to 1232 °C). |
| Weld joint strengthlow severity | Welding high-strength joints without post-weld heat treatmentAalco recommends post-weld hardening and tempering for high-strength joints, with preheat at 150 to 320 °C and post-heat at 610 to 760 °C. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Magnetic response of parts and assemblies | 420 is magnetic, in both the annealed and hardened condition, so it cannot be used where a nonmagnetic material is required. |
Handling and storage
- Specify the temper with the order: strength and hardness follow the tempering temperature, from 255.2 ksi tensile at 440 °F to 158.5 ksi at 1000 °F (Rolled Alloys table).
- Harden and temper after fabrication. The supplier's thermal-treatment table gives hardening at 950 to 1050 °C with oil, polymer or air cooling, and tempering at 600 to 700 °C or 650 to 750 °C.
Mitigations
- Ventilate or enclose cutting, grinding and welding to limit dust and fume, as the generic stainless SDS advises.
Supply and geography
How common the raw materials are and where they come from.
Chromium (mine production, the alloying element in 420)
- Top producers (2025)
- South Africa 45.1%, Turkey 17.6%, Kazakhstan 13.7%
- Recycling
- USGS: in 2025 recycled chromium contained in stainless-steel scrap receipts accounted for 21 % of apparent consumption. The United States imported 79 % of its apparent consumption (2025e net import reliance).
- Substitutes
- USGS: chromium has no substitute in stainless steel, the leading end use, or in superalloys. Chromium-containing scrap can substitute for ferrochromium in some metallurgical uses.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
spore: profile
id: stainless-420
spore_version: 0.2
family: stainless-martensitic
name: Stainless steel 420
abbreviation: '420'
role: hardenable martensitic stainless steel for blades, bearings and wear parts
category: metals
type: steels-and-stainless
summary: |
AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon (EN composition). Annealed, its maximum hardness is 241 HB and its yield strength 51.5 ksi. Tempered at 440 °F it reaches a yield strength of 190.1 ksi and 48 HRC. Its density is 7.75 g/cm3, it is magnetic, and it resists corrosion less well than the ferritic and austenitic steels. Tempered at 1000 °F its tensile strength falls to 158.5 ksi.
best_for: Hardened wear parts, blades and bearing-type components that need high strength and edge retention, from one steel that reaches 48 HRC after tempering at 440 °F
weakest_at: 'Corrosion resistance and ductility: it resists corrosion less well than austenitic grades, and it loses strength when tempered at 1000 °F (158.5 ksi tensile)'
identity:
formula: 'Iron-chromium-carbon steel: Fe balance, Cr 12.0 to 14.0 %, C 0.16 to 0.25 % (EN 1.4021 composition)'
source: teamedelstahl-1-4021
where: Chemical composition table, 1.4021 (X20Cr13 / AISI 420) page
designations:
- system: UNS
code: S42000
source: rolledalloys-420
where: Specifications box, UNS line
- system: EN
code: '1.4021'
source: rolledalloys-420
where: Specifications box, W. Nr./EN line
- system: EN name
code: X20Cr13
source: teamedelstahl-1-4021
where: Standards and nomenclature section, page heading 1.4021 (X20Cr13 / AISI 420)
- system: AISI
code: '420'
source: teamedelstahl-1-4021
where: Standards and nomenclature section, page heading 1.4021 (X20Cr13 / AISI 420)
- system: ASTM
code: A276
note: listed specification for Type 420
source: rolledalloys-420
where: Specifications box, ASTM line
- system: ASTM
code: A484
note: listed specification for Type 420
source: rolledalloys-420
where: Specifications box, ASTM line
- system: AMS
code: '5621'
source: rolledalloys-420
where: Specifications box, AMS line
tags:
environments: []
stresses:
- corrosion
applications:
- mechanisms
properties:
- benchmark: density
label: Density, 1.4021 bar (EN 10088-3)
value: 7.75
unit: g/cm3
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
standard: EN 10088-3:2005
temperature: not stated
method: Value printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Physical Property table, row Density
- benchmark: density
label: Density, 1.4021 / AISI 420 (20 °C)
value: 7.7
unit: kg/dm3
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
method: Value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Physical properties at 20 °C table, row Density
- benchmark: density
label: Density, Type 420 (ASTM A276)
value: 0.278
unit: lb/in3
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: not stated
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Density
- benchmark: melting_point
label: Melting range, Type 420
value: 2650
value_high: 2750
bound: range
unit: °F
scope: material
conditions:
grade: Type 420, UNS S42000
unit_in_source: 2650 - 2750 °F
method: Range printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Melting Range
- benchmark: poissons_ratio
label: Poisson's ratio, Type 420
value: 0.28
unit: '-'
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: not stated
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Poisson Ratio
- benchmark: elastic_modulus
label: Modulus of elasticity, 1.4021 bar
value: 200
unit: GPa
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
standard: EN 10088-3:2005
temperature: not stated
method: Value printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Physical Property table, row Modulus of Elasticity
- benchmark: elastic_modulus
label: Modulus of elasticity, 1.4021 (20 °C)
value: 215
unit: kN/mm2
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
method: Value printed in a steel supplier's material page
status: ground
note: The other two sources give 200 GPa (Aalco) and 31.2 x 10^6 psi, which is about 215 GPa; the 200 GPa figure is a separate row.
source: teamedelstahl-1-4021
where: Mechanical properties at 20 °C table, row Modulus of elasticity
- benchmark: elastic_modulus
label: Modulus of elasticity, Type 420 (68 °F)
value: 31.2
unit: 10^6 psi
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: 68 °F
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Modulus of Elasticity (68°F)
- benchmark: thermal_conductivity
label: Thermal conductivity, 1.4021 bar
value: 24.9
unit: W/(m·K)
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
temperature: not stated
method: Value printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Physical Property table, row Thermal Conductivity
- benchmark: thermal_conductivity
label: Thermal conductivity, 1.4021 (20 °C)
value: 30
unit: W/(m·K)
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
method: Value printed in a steel supplier's material page
status: ground
note: 'Two sources differ: 24.9 W/(m·K) (Aalco, temperature not stated) and 30 W/(m·K) at 20 °C (teamedelstahl). Both are kept with their conditions.'
source: teamedelstahl-1-4021
where: Physical properties at 20 °C table, row Thermal conductivity
- benchmark: thermal_conductivity
label: Thermal conductivity, Type 420 (212 °F)
value: 14.4
unit: BTU/(hr·ft·°F)
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: 212 °F
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Thermal Conductivity (212°F)
- benchmark: cte
label: Coefficient of thermal expansion, 1.4021 bar (0 to 100 °C)
value: 10.3
unit: 10^-6/K
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
temperature_range: not stated in the Aalco table
method: Value printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Physical Property table, row Thermal Expansion
- benchmark: cte
label: Coefficient of thermal expansion, Type 420 (68 to 212 °F)
value: 5.833
unit: µin/in·°F
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: 68 to 212 °F
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Coefficient of Thermal Expansion (68°F - 212°F)
- benchmark: specific_heat
label: Specific heat capacity, 1.4021 (20 °C)
value: 460
unit: J/(kg·K)
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
method: Value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Physical properties at 20 °C table, row Specific heat capacity
- benchmark: electrical_resistivity
label: Electrical resistivity, 1.4021 bar
value: 0.55
unit: µΩ·m
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
unit_in_source: x10^-6 Ω.m
temperature: not stated
method: Value printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Physical Property table, row Electrical Resistivity
- benchmark: electrical_resistivity
label: Electrical resistivity, 1.4021 (20 °C)
value: 0.6
unit: Ω·mm2/m
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
method: Value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Physical properties at 20 °C table, row Electrical resistance
- benchmark: electrical_resistivity
label: Electrical resistivity, Type 420
value: 25.6
unit: µΩ·in
scope: material
conditions:
grade: Type 420, UNS S42000
temperature: not stated
method: Value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Physical Properties, row Electrical Resistivity
- benchmark: yield_strength
label: Yield strength 0.2 % offset, Type 420 annealed (Condition A)
value: 51.5
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: annealed (Condition A, ASTM A276)
measure: 0.2 % yield strength
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row Annealed, column 0.2% Yield Strength
- benchmark: yield_strength
label: Yield strength 0.2 % offset, Type 420 tempered at 440 °F
value: 190.1
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 440 °F
measure: 0.2 % yield strength
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row 440, column 0.2% Yield Strength
- benchmark: yield_strength
label: Yield strength 0.2 % offset, Type 420 tempered at 1000 °F
value: 137.9
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 1000 °F
measure: 0.2 % yield strength
method: Value printed in a mill datasheet, tempered-condition table
status: ground
note: 'Over-tempering: the same table gives 36 HRC at this temper, against 48 HRC at 440 °F.'
source: rolledalloys-420
where: Tempered Condition Properties table, row 1000, column 0.2% Yield Strength
- benchmark: yield_strength
label: Proof stress Rp0.2, 1.4021 bar up to 160 mm
value: 500
value_high: 600
bound: range
unit: MPa
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
standard: EN 10088-3:2005
temper: not stated
method: Range printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Mechanical Property table under Spec EN 10088-3:2005, row Proof Stress
- benchmark: yield_strength
label: Yield strength Rp0.2, 1.4021 (20 °C) lower limit
value: 460
bound: lower
unit: N/mm2
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
temper: not stated
method: Minimum value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Mechanical properties at 20 °C table, row Yield point Rp0.2
- benchmark: ultimate_tensile_strength
label: Tensile strength, Type 420 annealed (Condition A)
value: 85.8
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: annealed (Condition A, ASTM A276)
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row Annealed, column Ultimate Tensile Strength
- benchmark: ultimate_tensile_strength
label: Tensile strength, Type 420 tempered at 440 °F
value: 255.2
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 440 °F
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row 440, column Ultimate Tensile Strength
- benchmark: ultimate_tensile_strength
label: Tensile strength, Type 420 tempered at 1000 °F
value: 158.5
unit: ksi
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 1000 °F
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row 1000, column Ultimate Tensile Strength
- benchmark: ultimate_tensile_strength
label: Tensile strength Rm, 1.4021 bar up to 160 mm
value: 700
value_high: 950
bound: range
unit: MPa
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
standard: EN 10088-3:2005
temper: not stated
method: Range printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Mechanical Property table under Spec EN 10088-3:2005, row Tensile Strength
- benchmark: ultimate_tensile_strength
label: Tensile strength Rm, 1.4021 (20 °C)
value: 750
value_high: 850
bound: range
unit: N/mm2
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
temper: not stated
method: Range printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Mechanical properties at 20 °C table, row Tensile strength Rm
- benchmark: elongation
label: Elongation A, 1.4021 bar up to 160 mm
value: 12
value_high: 13
bound: range
unit: '%'
scope: material
conditions:
grade: 1.4021 (420) bar, up to 160 mm
standard: EN 10088-3:2005
temper: not stated
method: Range printed in a stockholder datasheet
status: ground
source: aalco-1-4021
where: Mechanical Property table under Spec EN 10088-3:2005, row Elongation A
- benchmark: elongation
label: Elongation A5.65, 1.4021 (20 °C) lower limit
value: 12
bound: lower
unit: '%'
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
temper: not stated
method: Minimum value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Mechanical properties at 20 °C table, row Elongation A5,65
- benchmark: hardness_brinell
label: Hardness Brinell maximum, Type 420 annealed (Condition A)
value: 241
bound: upper
unit: HB
scope: material
conditions:
grade: Type 420, UNS S42000
temper: annealed (Condition A, ASTM A276)
method: Maximum value printed in a mill datasheet
status: ground
source: rolledalloys-420
where: Mechanical Properties, row Hardness MAX, Brinell (Condition A footnote)
- benchmark: hardness_brinell
label: Hardness Brinell maximum, 1.4021 (20 °C)
value: 230
bound: upper
unit: HB
scope: material
conditions:
grade: 1.4021 (X20Cr13 / AISI 420)
temperature: 20 °C
temper: not stated
method: Maximum value printed in a steel supplier's material page
status: ground
source: teamedelstahl-1-4021
where: Mechanical properties at 20 °C table, row Hardness HB
- benchmark: hardness_rockwell_c
label: Hardness Rockwell C, Type 420 tempered at 440 °F
value: 48
unit: HRC
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 440 °F
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row 440, column Rockwell Hardness HRC
- benchmark: hardness_rockwell_c
label: Hardness Rockwell C, Type 420 tempered at 1000 °F
value: 36
unit: HRC
scope: material
conditions:
grade: Type 420, UNS S42000
temper: tempered at 1000 °F
method: Value printed in a mill datasheet, tempered-condition table
status: ground
source: rolledalloys-420
where: Tempered Condition Properties table, row 1000, column Rockwell Hardness HRC
- benchmark: max_service_temp
label: Scaling resistance limit, continuous (1.4021)
value: 675
bound: upper
unit: °C
scope: material
conditions:
grade: 1.4021 (420)
basis: scaling resistance, continuous
intermittent_limit: 760 °C
note_in_source: use above the tempering temperature is not recommended if mechanical properties must be kept
method: Value printed in a stockholder datasheet, corrosion resistance section
status: ground
note: A scaling limit, not a structural service limit. The Aalco page says mechanical properties fall above the tempering temperature.
source: aalco-1-4021
where: Corrosion Resistance section, Heat resistance paragraph
corrosion:
- environment: Air and humid atmospheres
headline: Martensitic steels resist corrosion less well than ferritic and austenitic grades because their chromium is low.
effect: Wikipedia says martensitic stainless steels are not as corrosion-resistant as ferritic and austenitic grades due to their low chromium content, and lists Type 420 as a representative grade. Rolled Alloys says 420 offers corrosion resistance comparable to that of Type 410.
rating: moderate
conditions:
basis: general comparison; no corrosion rate or test environment given in the sources
source: wikipedia-stainless
where: Families, Martensitic section
- environment: Hardened condition
headline: Maximum corrosion resistance is reached in the fully hardened condition, not the annealed one.
effect: Aalco states that maximum corrosion resistance is achieved in the hardened condition, and the Rolled Alloys sheet describes 420 as similar to 410 in corrosion resistance. No corrosion rate is given.
rating: moderate
conditions:
basis: qualitative statement; no test environment given
source: aalco-1-4021
where: Corrosion Resistance section
- environment: High-temperature scaling in air
headline: 420 scales in air at high temperature, with a continuous limit of 675 °C.
effect: Aalco gives fair scaling resistance up to 760 °C intermittently and 675 °C continuously, and says use above the tempering temperature is not recommended if mechanical properties must be kept.
rating: moderate
conditions:
basis: scaling resistance in air; no weight-gain or rate values given
source: aalco-1-4021
where: Corrosion Resistance section, Heat resistance paragraph
risks:
hazards:
- text: 'Generic stainless steel SDS (Parker Steel, Metric Metal), not a 420-specific sheet: solid metal products are generally articles and not hazardous materials under the OSHA Hazard Communication Standard. Small chips, fines and dust may ignite readily, and hazardous elements can be released during cutting, grinding and welding. Do not breathe dust or fume.'
ghs: []
source: metric-sds
where: Section 2 Hazards Identification, General Hazard Statement and Hazard Statements; generic SDS, GHS classes not applied to 420 here
- text: Welding, torch cutting or grinding of stainless steel can generate hexavalent chromium. The SDS notes that chromium metal in the zero valence state does not present an unusual health hazard.
ghs: []
source: metric-sds
where: Asterisked footnote to the composition table on chromium metal
failure_risks:
- mode: Loss of strength from over-tempering
trigger: Tempering or service at 1000 °F (538 °C)
consequence: The Rolled Alloys table gives 158.5 ksi tensile and 137.9 ksi yield at 1000 °F, against 255.2 ksi tensile at 440 °F, and 36 HRC against 48 HRC. Aalco also warns of strength loss from over-tempering at elevated temperature.
severity: high
source: rolledalloys-420
where: Tempered Condition Properties table, rows 440 and 1000; Aalco Temperature notes
- mode: Brittleness at sub-zero temperature
trigger: Service below zero degrees Celsius
consequence: Aalco says the useful temperature range is limited by loss of ductility below zero.
severity: moderate
source: aalco-1-4021
where: Operating range paragraph, Temperature notes
- mode: Cracking during hot working
trigger: Hot working below 1700 °F (927 °C)
consequence: Aalco says hot work below 1700 °F may cause cracking; work should start after uniform heating to 2100 to 2250 °F (1149 to 1232 °C).
severity: moderate
source: aalco-1-4021
where: Hot working paragraph, Temperature notes
- mode: Weld joint strength
trigger: Welding high-strength joints without post-weld heat treatment
consequence: Aalco recommends post-weld hardening and tempering for high-strength joints, with preheat at 150 to 320 °C and post-heat at 610 to 760 °C.
severity: low
source: aalco-1-4021
where: Weldability section
side_effects:
- text: 420 is magnetic, in both the annealed and hardened condition, so it cannot be used where a nonmagnetic material is required.
affects: Magnetic response of parts and assemblies
source: wikipedia-stainless
where: Properties, Magnetism section; Families, Martensitic section
handling:
- text: 'Specify the temper with the order: strength and hardness follow the tempering temperature, from 255.2 ksi tensile at 440 °F to 158.5 ksi at 1000 °F (Rolled Alloys table).'
source: rolledalloys-420
where: Tempered Condition Properties table
- text: Harden and temper after fabrication. The supplier's thermal-treatment table gives hardening at 950 to 1050 °C with oil, polymer or air cooling, and tempering at 600 to 700 °C or 650 to 750 °C.
source: teamedelstahl-1-4021
where: Thermal treatment table
mitigations:
- text: Ventilate or enclose cutting, grinding and welding to limit dust and fume, as the generic stainless SDS advises.
source: metric-sds
where: Engineering controls paragraph in the handling section
uses:
- application: mechanisms
device: Bearings and industrial chains
example: Rolled Alloys lists industrial chains and bearings among the applications of Type 420, which it says is used for high strength, high wear resistance or good edge retention.
source: rolledalloys-420
where: Applications list
- application: mechanisms
device: Pumps and valves
example: Rolled Alloys lists pumps and valves, and plastic injection moulds and dies, among the applications of Type 420.
source: rolledalloys-420
where: Applications list
supply:
- subject: Chromium (mine production, the alloying element in 420)
producers:
- country: South Africa
share_percent: 45.1
year: 2025
- country: Turkey
share_percent: 17.6
year: 2025
- country: Kazakhstan
share_percent: 13.7
year: 2025
critical_lists: []
recycling: 'USGS: in 2025 recycled chromium contained in stainless-steel scrap receipts accounted for 21 % of apparent consumption. The United States imported 79 % of its apparent consumption (2025e net import reliance).'
substitutes:
- 'USGS: chromium has no substitute in stainless steel, the leading end use, or in superalloys. Chromium-containing scrap can substitute for ferrochromium in some metallurgical uses.'
source: usgs-mcs2026-chromium
where: 'World Mine Production and Reserves table, 2025e column (world total 51,000 thousand t, gross weight: South Africa 23,000, Turkey 9,000, Kazakhstan 7,000); shares calculated by Space Mushroom from those values; Recycling; Substitutes; Domestic Production and Use'
documents:
- title: Rolled Alloys data sheet 420 (UNS S42000, W. Nr./EN 1.4021), 2022
type: datasheet
url: https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf
year: 2022
- title: Aalco datasheet, Stainless Steel 1.4021 (420) Bar
type: datasheet
url: https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx
- title: teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)
type: datasheet
url: https://www.teamedelstahl.de/en/materials/1-4021/
- title: Righton Blackburns datasheet, Stainless Steel 1.4021 (420) Bar
type: datasheet
url: https://www.rightonblackburns.co.uk/datasheets/view/stainless-steel-1-4021-420-bar
- title: 'USGS Mineral Commodity Summaries 2026: Chromium'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
year: 2026
- title: Metric Metal safety data sheet, Stainless Steels (Parker Steel, issue 2/1/2016)
type: sds
url: https://www.metricmetal.com/wp-content/uploads/2018/08/G-SDS-Stainless-Steel.pdf
year: 2016
- title: 'Wikipedia: Martensitic stainless steel'
type: database
url: https://en.wikipedia.org/wiki/Martensitic_stainless_steel
- title: 'Wikipedia: Stainless steel'
type: database
url: https://en.wikipedia.org/wiki/Stainless_steel
gaps:
- Atomic weights for the recipe parts (Fe, Cr, C) were not read from a fetched page, so the recipe gives weight shares only.
- No primary ASTM A276 or EN 10088-3 table was opened; the mechanical values come from a stockholder page (Aalco), a supplier page (teamedelstahl) and a mill sheet (Rolled Alloys), each for a different temper or product size.
- The Aalco page describes its bar as a sulphur-enhanced machining grade. The sulphur figure (0.030 % maximum) is the same as the other sources, but the free-machining claim was not checked against a second source.
- Heat-treated hardness for 1.4021 (quench plus temper) in HRC was not found in a 1.4021-specific source. The 45 to 50 HRC and 52 to 55 HRC figures seen on other pages are for a different grade (420J1) or are not tied to a grade, so they are not used.
- Tensile and yield values from the Saky Steel SUS 420 table (650 MPa max) conflict with the EN figures (700 to 950 MPa) and are for a JIS grade with a different carbon range; they are not used.
- Atlas Quality Management, makeitfrom.com (403), the Combined Metals PDF and the Timken SDS could not be read in this run.
- No ISO 9223 corrosion rate, salt-spray result or pitting test for 420 was found in a fetched source.
- No cryogenic, impact (Charpy) or fatigue values for 420 were found in a fetched source.
- Radiation, outgassing, atomic oxygen and cold-welding data for 420 in vacuum were not looked up.
- The USGS 2026 chromium summary does not state whether chromium is on the U.S. critical minerals list, so critical_lists is empty.
- Hardness is recorded as hardness_brinell and hardness_rockwell_c because the canonical file has no hardness entry; these names are not in the canonical list.
- No PubChem or Wikipedia GHS record for the alloy was opened; the PubChem chromium page was blocked by a CAPTCHA.
sources:
rolledalloys-420:
title: Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22
url: https://rolledalloys.com/wp-content/uploads/420_DS_USA.pdf
year: 2022
kind: datasheet
license: Manufacturer data sheet, no warranty (cited, not reproduced)
aalco-1-4021:
title: Aalco Stainless Steel 1.4021 (420) Bar datasheet
url: https://www.aalco.co.uk/datasheets/Stainless-Steel-14021-420-Bar_311.ashx
kind: datasheet
license: Stockholder datasheet (cited, not reproduced)
teamedelstahl-1-4021:
title: teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420)
url: https://www.teamedelstahl.de/en/materials/1-4021/
kind: datasheet
license: Supplier material page (cited, not reproduced)
rightonblackburns-1-4021:
title: Righton Blackburns datasheet, Stainless Steel 1.4021 (420) Bar
url: https://www.rightonblackburns.co.uk/datasheets/view/stainless-steel-1-4021-420-bar
kind: datasheet
license: Stockholder datasheet (cited, not reproduced)
usgs-mcs2026-chromium:
title: Mineral Commodity Summaries 2026, Chromium
id: USGS MCS 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
year: 2026
kind: report
license: public domain (USGS)
metric-sds:
title: Metric Metal safety data sheet, Stainless Steels (Parker Steel), issue 2/1/2016
url: https://www.metricmetal.com/wp-content/uploads/2018/08/G-SDS-Stainless-Steel.pdf
year: 2016
kind: datasheet
license: Manufacturer safety data sheet (cited, not reproduced)
wikipedia-martensitic:
title: 'Wikipedia: Martensitic stainless steel'
url: https://en.wikipedia.org/wiki/Martensitic_stainless_steel
kind: web
license: CC BY-SA 4.0 (cited, not reproduced)
wikipedia-stainless:
title: 'Wikipedia: Stainless steel (Families and Properties sections)'
url: https://en.wikipedia.org/wiki/Stainless_steel
kind: web
license: CC BY-SA 4.0 (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-25'
review:
status: draft
method: assistant
checked_values: 37
unreachable: 4
caveats: 6
note: 'Values were read by an AI assistant on 2026-10-25 from the pages and PDFs named in each entry. The Rolled Alloys sheet was read from the PDF text. Unreachable in this run: Atlas Quality Management PDF, makeitfrom.com (403), Combined Metals PDF (image-only), Timken SDS (HTML). Caveats: values differ between sources and tempers; the Rolled Alloys tempering table uses ksi; the Metric Metal SDS is generic stainless and not 420-specific; the Aalco bar is sulphur-enhanced; hardness names are not canonical.'
story:
risk_groups:
- title: For people
lead: The sources describe a generic stainless steel SDS for solid stock, and the risk comes from dust, fume and processing rather than from the solid.
level: 1
verdict: Low for solid stock, higher for dust and fume
points:
- label: Solid stock
line: A generic stainless steel SDS says solid metal articles are generally not hazardous materials under the OSHA Hazard Communication Standard. Small chips, fines and dust may ignite readily.
- label: Processing
line: Cutting, grinding and welding can release hazardous elements, and welding or grinding can generate hexavalent chromium. Ventilation is the control the SDS names.
- title: If it fails
lead: The failure routes in the sources are about temper and temperature, not about a single corrosion rate.
points:
- label: Over-tempering
line: Tempered at 1000 °F, 420 falls to 158.5 ksi tensile and 36 HRC, against 255.2 ksi and 48 HRC at 440 °F (Rolled Alloys).
- label: Sub-zero service
line: Aalco says ductility is lost below zero, which limits the useful range.
- label: Corrosion
line: Wikipedia says martensitic steels resist corrosion less well than ferritic and austenitic grades. Aalco says maximum corrosion resistance is reached in the hardened condition.
- title: Handling and storage
points:
- label: Keep the temper in view
line: Strength and hardness follow the tempering temperature. The order should name the temper.
- label: Welds
line: Aalco recommends preheat at 150 to 320 °C and post-heat at 610 to 760 °C for high-strength joints.
why: AISI 420 (UNS S42000, EN 1.4021) is a martensitic stainless steel with 12.0 to 14.0 % chromium and 0.16 to 0.25 % carbon. The carbon lets it be hardened, so it reaches about 48 HRC after tempering at 440 °F (Rolled Alloys), while annealed it is soft, at most 241 HB. Its density is 7.75 g/cm3, and it is magnetic. It is chosen where a steel must be hard and wear-resistant and still stainless enough for blades, chains, bearings and valves. Its weak points are corrosion resistance, which is lower than that of austenitic steels, and strength loss if it is over-tempered.
uses:
- where: Bearings and chains
line: Rolled Alloys lists industrial chains and bearings among the applications of Type 420, which is used for high strength, high wear resistance or good edge retention.
- where: Pumps and valves
line: Rolled Alloys lists pumps and valves, and plastic injection moulds and dies, among the applications of Type 420.
can_do:
- label: Carry load when hard
value: 255.2 ksi tensile
benchmark: ultimate_tensile_strength
line: Tempered at 440 °F, Type 420 has a tensile strength of 255.2 ksi and a yield strength of 190.1 ksi (Rolled Alloys tempered-condition table).
- label: Stay hard
value: 48 HRC
benchmark: hardness_rockwell_c
line: The same tempered condition gives 48 HRC. Tempering at 1000 °F drops this to 36 HRC.
- label: Soft to form
value: 241 HB maximum
benchmark: hardness_brinell
line: Annealed (Condition A), the maximum hardness is 241 HB, and the yield strength is 51.5 ksi.
- label: Weight
value: 7.75 g/cm3
benchmark: density
line: Density is 7.75 g/cm3 in the Aalco datasheet, and 7.7 kg/dm3 at 20 °C in the teamedelstahl page.
- label: Heat to 675 °C
value: 675 °C continuous
benchmark: max_service_temp
line: Aalco gives a scaling limit of 675 °C continuous and 760 °C intermittent. This is a scaling limit; above the tempering temperature the mechanical properties fall.
compare: 'Among the stainless steels, 420 trades corrosion resistance for hardness: Wikipedia says martensitic steels are less corrosion-resistant than ferritic and austenitic grades. Its density of 7.75 g/cm3 (Aalco) is close to the value of 7.7 kg/dm3 given by teamedelstahl for the same grade. The compare rows use the figures printed by the sources, not a ranking of different alloys.'
compare_rows:
- label: Density
benchmark: density
- label: Thermal conductivity
benchmark: thermal_conductivity
- label: Thermal expansion
benchmark: cte
handling:
- Specify the temper, because strength and hardness follow the tempering temperature (Rolled Alloys table).
- Harden and temper after fabrication, following the thermal-treatment table (hardening 950 to 1050 °C, then tempering).
- Keep tempering below 1000 °F for useful strength, since 1000 °F tempering drops tensile strength to 158.5 ksi.
- Ventilate cutting, grinding and welding to limit dust and fume.
good_for:
- 'Hard, wear-resistant parts: 48 HRC after tempering at 440 °F (Rolled Alloys).'
- 'Stainless service with a magnetic response: 420 is magnetic in both conditions (Wikipedia).'
- Scaling in air up to 675 °C continuous (Aalco).
watch_out:
- 'Corrosion: lower than that of austenitic grades, and best in the hardened condition (Aalco, Wikipedia).'
- Over-tempering at 1000 °F drops tensile strength to 158.5 ksi.
- Sub-zero ductility is lost (Aalco), so brittle failure is a risk in cold service.
- Sources differ on thermal conductivity (24.9 W/(m·K) against 30 W/(m·K)) and modulus (200 GPa against 215 GPa).
verdict: AISI 420 (UNS S42000, EN 1.4021) is a hardenable stainless steel for blades, chains, bearings and valves. It reaches 48 HRC when tempered at 440 °F, weighs 7.75 g/cm3 and is magnetic. It resists corrosion less well than austenitic steels and loses strength when over-tempered. This profile lacks a 1.4021-specific corrosion rate, impact values and vacuum data.
recipe:
line: Martensitic stainless steel of iron with about 12 to 14 % chromium and 0.16 to 0.25 % carbon (EN 1.4021 composition). The steel is hot-worked after uniform heating to 1149 to 1232 °C (Aalco), then hardened and tempered (teamedelstahl).
parts:
- name: Iron
symbol: Fe
share: balance
role: Matrix of the steel
- name: Chromium
symbol: Cr
share: 12.0 to 14.0 wt%
role: Gives the steel its stainless character; low chromium makes it less corrosion-resistant than ferritic and austenitic grades (Wikipedia)
- name: Carbon
symbol: C
share: 0.16 to 0.25 wt%
role: Makes the steel hardenable; gives higher heat-treated strength at some cost in ductility (Rolled Alloys)
- name: Manganese
symbol: Mn
share: up to 1.5 wt%
role: Maximum allowed in the composition (teamedelstahl composition table)
- name: Silicon
symbol: Si
share: maximum listed in the composition table
role: Maximum allowed in the composition (teamedelstahl composition table)
- name: Sulphur
symbol: S
share: up to 0.030 wt%
role: Limit on the impurity; Aalco describes its bar as sulphur-enhanced for machining
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Rolled Alloys Data Sheet, 420 (UNS S42000, W. Nr./EN 1.4021, ASTM A276), rev. 11/22 | datasheet | 2022 | 20 values | |
| Aalco Stainless Steel 1.4021 (420) Bar datasheet | datasheet | 14 values | ||
| teamedelstahl material page, 1.4021 (X20Cr13 / AISI 420) | datasheet | 11 values | ||
| Righton Blackburns datasheet, Stainless Steel 1.4021 (420) Bar | datasheet | 0 values | ||
| Mineral Commodity Summaries 2026, Chromium | report | 2026 | 1 value | |
| Metric Metal safety data sheet, Stainless Steels (Parker Steel), issue 2/1/2016 | datasheet | 2016 | 3 values | |
| Wikipedia: Martensitic stainless steel | web | 0 values | ||
| Wikipedia: Stainless steel (Families and Properties sections) | web | 2 values |